Absorbers that attenuate or dampen vibrations are employed in a variety of applications where the isolation of one mass from another is preferred. These devices often use spring-like elements that may be categorized in a variety of types but as a rule exhibit a response characteristics to input loads known as spring rate. In applications where it is desirable to adjust or vary the response characteristics of the spring-like element, the accurate and effective control of the device presents a number of challenges.